It is known that stimulated emission can be produced in various organic solutions. The first such solutions were of dyes, as reported by Sorokin et al, IBM Journal, Volume II, page 130, Mar. 1967, and since then devices which have been used to produce such stimulated radiation have been commonly known as "dye lasers". Some materials which fluoresce or scintillate outside the visible spectrum also have been utilized. A compilation of materials which have served as the active medium in dye lasers is provided in the above cited article of Sorokin et al, and in the review of Kagan et al, Laser Focus, page 26, Sept. 1968.
United States Patents which describe dye lasers include U.S. Pat. Nos. 3,541,470; 3,679,995; 3,684,979; 3,818,371; 4,397,023; 4,603,422; and references cited therein.
Of particular interest with respect to the present invention is J. Am. Chem. Soc., 88(24), 5956(1984) by D. Avnir et al, which reports the production of a monolithic matrix of silica gel glass which has a content of embedded Rhodamine 6G. The translational, rotational and vibrational degrees of freedom of the trapped dye are reduced.
The characteristics of dye lasers which make them attractive are the possibilities of wide spectral range and tunability at low cost. The laser can be operated anywhere in the visible or into the ultraviolet or infrared simply by changing to a solution which emits at the desired spectral output.
The output wavelength of a dye laser also is tunable, either by varying the concentration of the solution, by varying the solvent, or by introducing a wavelength selective element such as a grating reflector into the optical cavity to control the emission wavelength. Significant spectral narrowing without significant energy reduction is an additional benefit obtained with the use of a grating reflector i.e., line widths less than 1 angstrom can be achieved in contrast to the 50-200 angstrom widths which are characteristic dye laser emission.
Typical dye lasers have been pumped with Q-switched ruby or glass lasers, or pumping has been accomplished with flash lamps. Pumping has been either in a longitudinal geometry, in which the pumping radiation is colinear with the optical cavity axis and stimulated radiation, or in a transverse geometry, with the excitation at right angles to this axis.
Dye lasers have not achieved their full potential because of various disadvantages such as (1) a number of useful materials are difficult to pump because of low quantum efficiency or high excited state losses due to singlet-triplet transitions or to triplet absorptions; (2) low conversion efficiencies, high coupling energy losses, and low repetition rates result due to thermal effects induced during pumping; and (3) dye circulation problems and limitations are posed by these thermal effects.
Accordingly, it is an object of this invention to provide an improved tunable lasing system.
It is another object of this invention to provide a dye laser which has low excited state losses, and is characterized by a high quantum efficiency.
It is a further object of this invention to provide a dye laser medium which has a solid matrix phase and a static dye solution phase.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.